With the increasing demand for portable computing devices and portable wireless computing devices, there has been considerable effort expended in the development of portable power supplies for such devices. The usual approach is to rely upon a battery pack that is periodically recharged from the mains supply. The battery pack typically includes a plurality of interlinked batteries in combination with protection circuitry to prevent the current provided by the batteries from exceeding a predetermined maximum operational current. If that minimum is exceeded, the protection circuitry isolates the batteries from the computing device. In some cases the circuitry also, after a delay, reconnects the batteries. In any case, the step of isolating the batteries from the device is that the device shuts dowry. Clearly, this is inconvenient to the user.
The load current drawn by computing devices varies greatly, and sharply, with time. This creates enormous voltage ripple for the battery pack. This, in turn, is not ideal for most batteries, many of which are best suited to provide steady current levels. Moreover, the peak load currents are often large in comparison to the average load current, although only of short duration. This requires that additional complexity be designed into the protection circuit to prevent undesirable triggering of that circuit.
There has been some evidence of the proposed use of supereapacitors to supply power to portable electronic devices, although as a source secondary to the battery pack. Such devices are usually accompanied by a second protection circuit to limit the flow of current to and from the supercapacitor. This circuitry tends to significantly degrade the effectiveness of the supercapacitor in these applications.
Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of common general knowledge in the field.